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The question is somewhat general-reference; a Google search for "swap king and rook" brings up the Wikipedia article on "Castling" as the first result, which would tell bigown all he'd need to know about the move and more. Stack Exchange is not supposed to be a substitution for Google; in fact the point is to supplement Google search results for similar queries to the questions asked.
–
KeithSOct 22 '14 at 14:59

5 Answers
5

It's called castling. It's important because it gets your king out of danger (the centre is not safe), while simultaneously moving your 'tower' (also called a Castle, or a Rook) into the centre, where it is much more useful.

The main advantage is that you move 2 at the same time. It's important to note that the 2 castlings are not the same. The long one is more aggressive and if you do it right, you get your rook in line with your queen.

Traditionally, taking the center should be an objective. Castling enables this.

I don't consider myself a strong player, but in my experience, Castling is best used for positioning rather as a defense for your King. Remember, you need to have the Initiative...

The main purpose of castling is to "develop" the king, not the rook. The king is easier to defend towards the end squares but can be in danger anywhere.

However around the e-file the king also gets in the way of the other pieces, in particular blocking the rook in. Thus the castling move "swaps" the positions of the king and rook simultaneously.

The normal sequence of opening moves is to first get minor pieces out and a few pawns, castle, get the queen out and that leaves the two rooks alone in the back-rank aside from the king near the end where they can move around freely between the files.

In highly "attacking" chess games, the two players may castle on opposite sides, i.e. one does the king-side and the other the queen-side. You then launch an attack on the side where the other play has his king by moving the pawns forward. However you also need to defend your own side from the opponents attack.

Such games often suit white better. I therefore once had a rule that if I was black I would wait for my opponent to castle first. I'm not sure about the general validity of that rule, but something to consider.